Carbon-graphite gas-bearing roll

ABSTRACT

A high speed, lightly loaded, externally pressurized gas bearing roll for use in the processing of yarns and the like is characterized by a lightweight, substantially impermeable, resin impregnated carbon-graphite rotatable shell mounted on a permeable carbon-graphite sleeve with an interposed externally pressurized gas film.

United States Patent Bird et al.

[ 5] Feb. 29, 1972 CARBON-GRAPHITE GAS-BEARING ROLL Inventors: Melvyn R. Bird, Huron; Paul J. Christiansen, Sandusky; Philip B. Zeigler, Fort Clinton, all of Ohio Assignee: General Motors Corporation, Detroit,

Mich.

Filed: Dec. 17, i970 Appl. No.: 99,159

[1.8. CI... ..308/9, 308/ I07 Int. Cl. ...Fl6c 17/16, Fl6c l3/02 FieldolSearch ..308/9, I07, I22

[56] References Cited UNITED STATES PATENTS 3,527,510 9/1970 Christiansen ..308/ I07 Primary Examiner- Edgar W. Geoghegan Assistant Examiner-Frank Susko Attorney-J. L. Carpenter and F. .l. Fodaif ABSTRACT A high speed, lightly loaded, externally pressurized gas bearing roll for use in the processing of yarns and the like is characterized by a lightweight. substantially impermeable. resin impregnated carbon-graphite rotatable shell mounted on a permeable carbon-graphite sleeve with an interposed externally pressurized gas film.

6 Claims, 4 Drawing Figures Patented Feb. 29, 1972 Phiap 5. &('gler z 7 ATTORNEY CARBON-GRAPHITE GAS-BEARING ROLL This invention relates generally to gas journal bearing rolls and more specifically to gas (usually air) joumal-bearing rolls of the externally pressurized, permeable sleeve compensated type, such as may be used for separator or idler rolls in textile drawing and spinning machinery and the like.

It is the object of the invention to provide an economical, etficient, externally pressurized roll having a penneable sleeve between the load bearing gas film and a supply plenum to regulate gas flow into the load bearing gas film in which provision is made for maintaining the gas bearing space over an appreciable temperature operational regime, in which the parts areprotected in the event of gas film failure.

The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawing in which:

FIG. 1 is an elevation partially in section of a roll in accordance with this invention;

FIG. 2 is a section taken along the line 22 of FIG. 1 and looking in the direction of the arrows;

FIG. 3 is a section taken along the line 3-3 of FIG. 1 and looking in the direction of the arrows; and

FIG. 4 is a section taken along the line 4-4 of FIG. 1 and looking in the direction of the arrows.

Referring now to the drawing and more specifically to FIG. 1, a separator roll indicated generally at 10 includes a hub 12, the undercut right-hand portion 14 of which is adapted to be mounted in a stationary manner on a textile drawing machine or the like. The hub 12 has a pair of spaced recesses 16, each with a pair of spaced grooves 18 which each receive a resilient rubber O-ring 20. A longitudinal blind-ended passage 22 leads from the right end of the hub l2 to the surfaces of the recesses 16 through radial passages 24. Mounted on the four spaced rings is a permeable sleeve 26. The permeable sleeve 26 is a carbon-graphite composition, such as Graphitar, Grade 2413, a material made by the United States Graphite Company of Saginaw, Michigan. The carbon-graphite material has excellent properties for this usage; such as a uniform porosity or permeability and a capability of operation as a dry bearing. However, a drawback of the material is its low-tensile strength which is in the neighborhood of l,000 p.s.i. Accordingly, the sleeve 26 must be mounted on the hub [2 in such a manner that little tensile stress is imparted to the sleeve. To this end, the sleeve is mounted on the four resilient O-rings, compressing them slightly in their grooves 18. The dimensioning of the hub 12 and the sleeve 26 is preferably such that there is a very slight radial play therebetween so that, in effect, the sleeve 26 is resiliently mounted on the O-rings. The resilient mounting has been considered beneficial in inhibiting halfspeed whirl, an instability phenomenon. See for instance the U.S. Pat. No. 3,360,309, issued to Donald A. Voorhies on Dec. 26, 1967, for a Self Aligning, Externally Pressurized Fluid Bearing, and the British Pat. No. 796,926, issued to the United Kingdom Atomic Energy Authority on Apr. 30, l958, for Improvements In Or Relating To Gas Lubricated Bearings."

The compression of the O-rings 20 provides effective sealing at the hub and sleeve surfaces, thereby making the plenums 16 substantially fluidtight. it should be noted that the use of the two plenums 16 provides a ready means for varying the radial flow with respect to the axial flow through the sleeve 26 when it is of uniform permeability in both the axial and radial direction. Thus, the gas flow can be optimized. The frictional engagement of the sleeve 26 by the resilient O-rings 20 is generally insufficient to insure that the sleeve 26 will not move axially relative to the hub 12, especially if the separator roll were placed in an environment which transferred vibration to the separator roll. To insure positive location, snap rings 28 are provided on either side of the sleeve 26.

The greater portion of the snap rings 28 are disposed in grooves 30 in the hub 12 with a very slight amount of the snap Surrounding the sleeve 26 is a roll shell 32 provided at each end with a thrust washer 34. The shell 32 and the thrust washers 34 are made from essentially the same material as the sleeve 26. In this case, these parts are made from a resin impregnated carbon-graphite, such as Graphitar, Grade 86, also available from the United States Graphite Company of Saginaw, Michigan. The resin impregnation increases the strength of the parts, reduces their porosity or permeability to a negligible amount, and yet the thermal expansion coefficient is substantially identical to that of the sleeve being 2.3 l0' in./in./F., compared to 2.3x l0 in./in./F.

The substantially matched thermal expansion coefficients is desirable because the performance of an externally pressurized gas bearing is highly dependent on the space between the relatively rotating parts in which the gas load carrying film is located. This space is shown at 36 in the drawings and is generally on the order of 0.001 in.lin. of diameter. With the thermal coefficients of expansion of the sleeve 26 and the shell 32 substantially identical, this space 36 is maintainable at a substantially constant value over a significant operating temperature regime.

As is well known, the rotatable shell 32 is supported on a gas film and centered between films supplied through the porous sleeve 26 and which exhaust out the passages 38 and 40 at the inner and outer margins of the thrust washers 34. See the U.S. Pat. No. 3,374,039, issued to Donald A. Voorhies for an Antifriction Bearing on Mar. 19, 1968, and U.S. Pat. No. 3,527,510, issued to Paul J. Christiansen on Sept. 8, I970, for an Anti-Hammer Device for Air Spindles, the teachings of which are incorporated herein by reference.

It is important to note that the inner margin of the thrust washers 34 is such that the shell 36 touches the sleeve 26 before the thrust washers 34 contact either die hub or the snap rings 30. This dimensioning is to insure an adequate exhaust for the gas and avoidance of air hammer, as well as to insure the running of the roll shell 32 on the sleeve 26 in the event of gas film failure. The gas film failure could be due to an overloading of the roll shell or a simple interruption of the gas supply from its source. In any event, the roll fabricated from the materials as set forth has successfully been operated under overloaded conditions for more than 500 hours without damages to the parts.

In fact, the load carrying capacity of the separator roll improved slightly when normal operation was resumed. This im provement is thought attributable to the polishing of each surface by the other during operation in an overloaded condition.

In instances where the principles of this invention area applied to a separator or idler roll for textile machinery in which a yarn filament or the like is wrapped around the outer circumference of the roll shell, it is preferable to provide a wearresistant ceramic coating on the shell 32, as for instance provided by flame spraying the outer surface of the shell with alumina-titania particles.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described for obvious modifications will occur to a person skilled in the art.

We claim:

I. A gas bearing roll comprising:

a stationary hub,

a pair of spaced, resilient O rings mounted on said hub,

a permeable, carbon-graphite sleeve having an inner surface mounted on said spaced, resilient O-rings such that said O-rings are compressed between said surface and said hub,

means on said hub to axially locate said penneable carbongraphite sleeve thereon,

passage means in said hub, having one end adapted to be fluidly connected to a source of pressurized gas, and the other end opening onto said inner surface between said O-rings,

a substantially impermeable carbon-graphite roll shell surrounding said permeable sleeve, with a space therebetween, the space being such that the carbon-graphite roll shell is rotatably supported on a film of pressurized gas permeating said permeable carbon-graphite sleeve when said one end of said passage means is connected to a source of pressurized gas, and

exhaust passage means leading from said space to the exterior of said roll shell.

2. The combination as defined in claim I wherein said sleeve has exposed radial faces and further including annular, substantially impermeable carbon-graphite thrust rings mounted on said roll shell, said thrust rings having a radial face spaced closely adjacent said exposed radial faces on said sleeve respectively and wherein said exhaust passage means includes a first exit passage at the inner margin of said thrust rings and a second exit passage at the outer margin of said thrust rings 3. A high-speed, lightly loaded gas bearing roll for use in processing yarn and the like, comprising:

a stationary hub,

a radially and axially permeable, low-tensile strength, lowfriction sleeve surrounding said hub,

a plurality of sets of spaced O-rings compressed between said hub and said sleeve and resiliently mounting said sleeve on said hub, with the radial end faces of said sleeve substantially unobstructed by said hub,

retention means on said hub operatively associated with said end faces to axially locate said sleeve on said hub,

a plenum formed by said sleeve, hub, and each set of spaced O-rirtgs,

passage means in said hub having an inlet exterior of said sleeve and leading to said plenums,

a lightweight, low-friction roll shell surrounding said sleeve with a sufficient space therebetween to provide pressurized grm film in the space to rotatably support the roll shell out of contact with the sleeve when said inlet is fluidly connected to a source of pressurized gas,

an annular thrust washer adjacent each end of the roll shell with a radial face on each thrust washer spaced from a radial face on said sleeve respectively, said sleeve, roll shell and thrust washers being made from a material having the same basic composition and substantially the same coefi'rcients of thermal expansion, and

exhaust passage means at the inner and outer marginsof the thrust washers.

4. The combination as defined in claim 3 wherein said roll shell and thrust washers are made from a substantially impermeable, resin impregnated, carbon-graphite, wherein said roll shell is coated with a ceramic on its outer surface and wherein said permeable sleeve is made from carbon-graphite.

5. An externally pressurized gas bearing comprising:

a stationary member including a radially and axially permeable carbomgraphite sleevelike portion having exposed radial faces,

a plenum opening onto one circumferential surface of said sleevelike portion, and

passage means having one end opening into said plenum means and the other end adapted to be fluidly connected to a source of pressurized gas, and a rotatable, substantially impermeable, resin impregnated carbon-graphite member, having a cylindrical surface circumjacent said other circumferential surface of said sleevelike member and being so spaced with respect to it such that said rotatable member is rotatably supported on a film of pressurized gas permeating said permeable sleevelike portion when said other end of said passage means is connected to a source of pressurized gas, and

exhaust passage means leading from the space between said sleevelike portion and said rotatable member.

6. The combination as defined in claim 5 further including annular substantially impermeable, resin impregnated carbongraphite thrust rings mounted on the cylindrical surface of said rotatable member, said annular rings having a radial face spaced closely adjacent said exposed radial faces on said sleevelike member, 

1. A gas bearing roll comprising: a stationary hub, a pair of spaced, resilient O-rings mounted on said hub, a permeable, carbon-graphite sleeve having an inner surface mounted on said spaced, resilient O-rings such that said Orings are compressed between said surface and said hub, means on said hub to axially locate said permeable carbongraphite sleeve thereon, passage means in said hub, having one end adapted to be fluidly connected to a source of pressurized gas, and the other end opening onto said inner surface between said O-rings, a substantially impermeable carbon-graphite roll shell surrounding said permeable sleeve, with a space therebetween, the space being such that the carbon-graphite roll shell is rotatably supported on a film of pressurized gas permeating said permeable carbon-graphite sleeve when said one end of said passage means is connected to a source of pressurized gas, and exhaust passage means leading from said space to the exterior of said roll shell.
 2. The combination as defined in claim 1 wherein said sleeve has exposed radial faces and further including annular, substantially impermeable carbon-graphite thrust rings mounted on said roll shell, said thrust rings having a radial face spaced closely adjacent said exposed radial faces on said sleeve respectively and wherein said exhaust passage means includes a first exit passage at the inner margin of said thrust rings and a second exit passage at the outer margin of said thrust rings.
 3. A high-speed, lightly loaded gas bearing roll for use in processing yarn and the like, comprising: a stationary hub, a radially and axially permeable, low-tensile strength, low-friction sleeve surrounding said hub, a plurality of sets of spaced O-rings compressed between said hub and said sleeve and resiliently mounting said sleeve on said hub, with the radial end faces of said sleeve substantially unobstructed by said hub, retention means on said hub operatively associated with said end faces to axially locate said sleeve on said hub, a plenum formed by said sleeve, hub, and each set of spaced O-rings, passage means in said hub having an inlet exterior of said sleeve and leading to said plenums, a lightweight, low-friction roll shell surrounding said sleeve with a sufficient space therebetween to provide pressurized gas film in the space to rotatably support the roll shell out of contact with the sleeve when said inlet is fluidly connected to a source of pressurized gas, an annular thrust washer adjacent each end of the roll shell with a radial face on each thrust washer spaced from a radial face on said sleeve respectively, said sleeve, roll shell and thrust washers being made from a material having the same basic composition and substantially the same coefficients of thermal expansion, and exhaust passage means at the inner and outer margins of the thrust washers.
 4. The combination as defined in claim 3 wherein said roll shell and thrust washers are made from a substantially impermeable, resin impregnated, carbon-graphite, wherein said roll shell is coated with a ceramic on its outer surface and wherein said permeable sleeve is made from carbon-graphite.
 5. An externally pressurized gas bearing comprising: a stationary member including a radially and axially permeable carbon-graphite sleevelike portion having exposed radial faces, a plenum opening onto one circumferential surface of said sleevelike portion, and passage means having one end opening into said plenum means and the other end adapted to be fluidly connected to a source of pressurized gas, and a rotatable, substantially impermeable, resin impregnated carbon-graphite member, having a cylindrical surface circumjacent said other circumferential surface of said sleevelike member and being so spaced with respect to it such that said rotatable member is rotatably supported on a film of pressurized gas permeating said permeable sleevelike portion when said other end of said passage means is connected to a source of pressurized gas, and exhaust passage means leading from the space between said sleevelike portion and said rotatable member.
 6. The combination as defined in claim 5 further including annular substantially impermeable, resin impregnated carbon-graphite thrust rings mounted on the cylindrical surface of said rotatable member, said annular rings having a radial face spaced closely adjacent said exposed radial faces on said sleevelike member. 